Foodstuffs are subject to chemical and biological processes which modify their composition and can also produce substances detrimental to health. For example, the foodstuffs may oxidise or they can be modified by enzymes and micro-organisms, such as mildew. In order that foodstuffs are safe for consumers to eat, can be transported and have the longest possible shelf life, these processes must be prevented or at least delayed within the desired shelf life.
One possibility is to apply a lot of sugar or salt to the foodstuff or to dry it in order to extract the water from the foodstuff and thus to impair the development of micro-organisms such as mildew or bacteria. Also the addition of alcohol, vinegar or preservatives as well as cooling retard the development of micro-organisms and reduce the activity of enzymes. Furthermore, heat treatment can ensure that micro-organisms are killed off and harmful enzymes rendered inactive. During pasteurisation the foodstuff is heated to about 100° C. for a certain period. However, the comparatively resistant bacterial spores continue to be germinable and there is the risk that important nutrients and aromas may be destroyed due to the heat treatment.
Another method of extending the shelf life of foodstuffs is to pack the foodstuff into a gas-tight package and to evacuate the package before closure. Optionally, an inert gas or protective mixtures can be added, for example nitrogen or CO2. Due to the displacement of air, for example of oxygen, the activity of enzymes or micro-organisms is also retarded.
A method at least so far hardly used on an industrial scale is the high pressure treatment of foodstuffs. With this method a normally already packed foodstuff is subjected to very high pressures of typically 400 MPa to 600 MPa over a certain time span, for example for a few minutes. These high pressures ensure that harmful micro-organisms in the foodstuff are destroyed and killed off. Smaller molecules however, such as vitamins, which determine the taste and nutritional value of the foodstuff, are hardly influenced by the high pressure treatment. With meat products the shelf life can be extended, for example, by a factor of six to ten in comparison to the untreated product.
Compared to heat treatment, high pressure treatment has various advantages. For example, the taste is hardly changed and the vitamin content in the foodstuff after high pressure treatment is often twice as high than after a heat treatment. Some heat-sensitive products, for example sea food, cannot be heat-treated at all. Pathogenic germs, such as listeria, can be reliably killed off, so that food safety is increased. High pressure treatment can however also specifically influence the internal structure of the foodstuff, so that novel product possibilities arise, for example, through the gelification of fruit preparations without heat. Finally, the technology regarding high pressure treatment is already recognised in many countries as safe (for food).
During the high pressure treatment of packaged foodstuffs problems can occur with the packaging due to the process conditions. For example, visually disadvantageous changes and also damage can occur. Particularly packages with an inert gas atmosphere give problems due to the significantly compressible gas content in the package. This is also one reason that so far mainly vacuum packaging has been used in high pressure treatment.
The inactivation of micro-organisms and the structural modification of foodstuff constituents are for example described in EP 0 588 010 A1, EP 0 689 391 B1, EP 0 752 211 B1, EP 1 100 340 B1, DE 42 26 255A1, and DE 37 34 025 C2. EP 1 112 008 B1, EP 1 201 252 B1, DE 196 49 952 A1, DE 197 38 800 A1, DE 199 39 677 A1 and DE 26 11 389 A1 describe the effects of the high pressure treatments on the microbiological shelf life and food safety. The use of high pressure treatment particularly on meat products is described in DE 198 01 031 C2, DE 196 53 677 C1, EP 0 748 592 B1, EP 0 683 986 B1, DE 101 01 958 A1, DE 10 2005 011 868 A1, or WO 2006/097248 A1.
A system for the high pressure treatment of foodstuffs is furthermore known from WO 2006/129180 A1. Here, an autoclave is provided with a high-pressure chamber in which the foodstuffs are subjected to a high pressure. The autoclave must be closed to establish the pressure. Consequently, the system cannot be operated continuously. In order to increase the throughput of the system it is typically operated using a batch method in which the products are introduced into the autoclave in groups, treated under high pressure and removed.
In order to be able to charge and discharge the autoclave more quickly and thus shorten the cycle time, the products to be treated are normally put into a container. When the high-pressure chamber is free, one or optionally several containers can be moved into the high-pressure chamber, for example in that the containers are moved by means of a slide. Following the high pressure treatment the containers are removed from the autoclave, for example, in that they are pushed out on the side opposite the entry opening.
A transport container for accommodating products during a high pressure treatment, which is limited with regard to filling, emerges from DE 199 52 611 A1. A generic container for the same purpose as the container of the present invention furthermore emerges from DE 10 2009 042 094 A1 or from EP 2 322 044 A1 which is parallel to it.
Containers, which are suitable for accommodating products during a temperature sterilisation, but would not withstand a high pressure treatment, are known for example from EP 0 165 152 A1, WO 95/24932 A1 or FR 2 542 200 A1. Further containers for completely different purposes, which would also not withstand a high pressure treatment, are known for example from DE 70 23 578, AT 365 150, DE 822 193, DE 72 07 545 or DE 91 09 207 U1.